Something's digging in the shredded bark, unearthing our shrubs/roses/perennials. What is it and what's it after? It's July in Michigan -- a little late for grubs, right?
Could be squirrels or chipmunks caching food for the winter, or robins looking for worms. If it has been dry in your area you will see unusual behaviour as animals look harder for food.
Try turning over the soil and seeing if there are grubs, that will bring in skunks and raccoons.